Well, I am 45 years old and never visited a high school, only college back in Germany...
Anyway. Wish to educate myself further and would like to find out how to get a online high school diploma in order to enter into the higher education field. Any online schools and university recommendations are much appreciated...

Thank you in advance

Accredited Online Colleges, Online Degrees and Distance Learning Programs
This seems like a good site. :) good for you to continue your education!

If you are in the US, please check any school against the list that the Dept of Education has, many of the ones on the above link supplied were not accredited and some appeared to be degree mills where you buy a fairly worthless degree.

To help where are you now living, what type of work have you done. You went to school in Germany, at what appeared to be post high school, did you have some education there ?

If you were attending college (did you leave with any sort of certificate?) in Germany, you won't need a high school diploma. Many universities now offer online courses (for both Bachelor's and Master's degrees) themselves. Depending on what state you are in, you can start with looking at the state universities' websites and see what they have to offer.

Another alternative would be a community college... many also offer online courses and you can get an Associates Degree that will transfer to a university so that you can complete your Bachelor's.